1. Field of the Invention
An apparatus for the selective removal of fatty tissue beneath the skin of an animal and, more particularly, to a handpiece for a power assisted suction lipectomy device.
2. Prior Art
Suction assisted lipectomy, a procedure originally developed in France, was introduced to the United States over a decade ago. Since then, the procedure has rapidly spread in popularity and consumer demand. The procedure involves anesthetizing a portion of the body containing unwanted fat deposits, introducing an apertured suction cannula beneath the skin into the unwanted fat and tearing the tissue apart by repeatedly jabbing the tip of the cannula into the tissue thereby mechanically breaking up (avulsing) the fat. The avulsed fat cells are then aspirated by suction means. Continuous reciprocal stroking of the cannula mechanically disrupts fatty tissue, allowing additional fat to be removed. The repetitive stroking movement of a cannula is both tiring for the physician and traumatic and uncomfortable for the patient who, notwithstanding anesthesia, experiences pain and discomfort with each thrust. Since fat from various different portions of the body is normally removed during the procedure, and further in view of the intense discomfort of the procedure, adequate local anesthesia of every fat-containing operative site may not be achieved.
Several liposuction cannulas, some disposable and some reusable, are commercially available. Liposuction cannulas are provided in different lengths and diameters, each having different slot or aperture dimensions to meet particular needs. Some apertures are configured in the "cobra head" configuration to increase the surface area of the cannula aperture while other cannulas have several openings on the side of the cannula. In each case the metal cannula is introduced into the (anesthetized) fat bearing target area through an incision in the skin. Powerful suction pulls some of the surrounding fat into the hollow cannula through one or more slots or apertures and the thrusting movement of the cannula avulses a portion of such fat. Adipose tissue has a low tensile strength compared to other tissues with which it is associated and the repetitive back and forth thrusting movement of the suction cannula preferably and differentially avulses large portions of fat from a given surgical area. This technique exploits the lower tensile strength of the fatty tissue and relatively spares the blood vessels from perforation since vascular structures comprise thicker collagen and have greater tensile strength than fatty tissue.
Numerous power assisted lipectomy devices have been developed. Some such power assisted devices employ mechanical shearing devices deployed at or near the distal tip of the cannula to cut the tissue. Others employ a cannula transmitting ultrasonic vibrations to the operative site to disperse or rupture the cells adjacent to the cannula. A power assisted suction lipectomy device employing a rotary member housed within a cannula is described by Swartz in U.S. Pat. No. 4,932,935, the teachings of which patent is hereby incorporated herein by reference thereto. Swartz, in the aforesaid '935 patent, discloses an improved lipectomy device which includes a cannula having an inner rotatably mounted tube and a concentric outer tube. The outer tube, the surface of which contacts the tissue during lipectomy, has an elongate slot in the wall thereof. The inner tube, which is rotatably mounted within the outer tube, has a spiral slot in the wall thereof A motor housed within the handle of the cannula rotates the inner tube within the outer tube by means of a worm drive. The spiral slot of the inner tube, which underlies the elongate slot on the outer tube, presents a "moving hole" when viewed from outside the cannula. The "moving hole" provides a moving aperture through which fatty tissue surrounding the cannula may enter the inner tube thereafter to be pulled apart from surrounding tissue. The avulsed tissue is aspirated from the operative site through the hollow interior of the inner tube of the cannula into a removal port by suction means.
In an alternate embodiment, Swartz (U.S. Pat. No. 4,932,935) discloses a cannula wherein the elongate slot in the outer cannula, which slot is disposed substantially coaxially with the long axis of the cannula, overlies a diagonal slot in the inner tube. Motor means within the handle of the cannula drives the inner tube in a rotary oscillatory motion with respect to the outer tube causing the "traveling hole" to move back and forth within the slot of the outer cannula rather than appearing at one end of the slot and disappearing at the other end only to reappear at the first end of the slot upon completion of a full rotation. The edges of the slots on both the inner and the outer tubes are provided with rounded edges to prevent unnecessary cutting of tissue. The rotund metal edges bordering the slots on the inner and the outer tubes pinch tissue which projects therebetween. This pinching and pulling avulses a portion of the tissue without applying sufficient force to avulse tissue having higher tensile strength. The Swartz device reduces trauma to the patient by preserving the integrity of non-target tissue while providing enhanced selectivity for removing fatty tissue.
The above described cannulas, with or without ultrasonic assistance, remain the mainstay of the suction lipectomy surgical instrumentarium and such improved cannulas allow the operating surgeon (through multiple strokes with the suction assisted cannula) to remove fat more or less differentially; sparing the larger blood vessels from injury. Although smaller blood vessels are traumatized by the force required for avulsion of fat and a certain amount of bleeding is expected, this elective procedure has generally proven itself to be relatively safe and effective in accomplishing the localized removal of fat in patients. Still, there exists a need for a power assisted liposuction handpiece which further reduces trauma to non-fatty tissue and is less tiring to use.